How to Construct a Pier and Beam Foundation

A pier and beam foundation can be used as a base to build any medium-sized, non-residential structure, such as a shed or a barn. In this DecorDezine article, we shall show you the step-by-step procedure for building a pier and beam foundation.

DecorDezine Staff

Important

Any foundation used to build an occupied structure such as a garage or a home requires strict adhering to design rules and regulations, obtaining permits, and usually includes inspections by officials. Hence, such foundations should be designed and built by professionals only.

DIY projects definitely help you learn a great deal, while at the same time you end up with something that has practical significance. In the following sections, we will take you through the steps for constructing a simple DIY pier and beam foundation. You are guaranteed to gain knowledge as you work towards perfecting your design, and also the final structure could be used as a base on which you can build useful structures, such as a tool shed or a hen coop, thus making the effort all the more worthwhile.

So put on your construction cap and get your toolbox ready, for it's time to hit the hammer on the nail.

Before you get your hands dirty, the first important step is to make a layout plan. This plan need not be like the complex and to-the-scale engineering drawings that civil engineers make. Just a rough sketch of the structure that you intend to build should suffice. Remember to mention the various dimensions though, including the length, width, and height of each structural element, along with the spacing between them, in your layout plan.

Note: Plan and layout creation requires a complete understanding of the entire building procedure. Hence, even though this is the first step, the layout plan should only be made after you have gone through all the steps described in this article. Also, while calculating the length and width of the foundation, do remember to figure in the width of each hole that you will be required to dig, as well as the spacing between two adjacent holes.

Step 2: Land Clearing and Perimeter Setup

The second step involves getting the construction site ready. For this, first, the chosen spot needs to cleared and prepared. Any stones, pieces of wood, plastic or glass bottles, large grass, weeds, etc., must be cleared from the spot. Small undulations in the ground must be leveled by digging off the lumps and filling in the voids.

The next important thing is to set up a perimeter for your project, using the wooden posts and the construction string. Install a wooden post in one corner of the construction plot. Then, using the measuring tape, measure a distance equal to the length of your structure, and fix another wooden post. Tie the construction string to the first post, and extend it up to the second one and wind it around it a couple of times. Now, perpendicular to the second post, measure a distance equal to the breadth of your structure, and fix the 3rd wooden post at that spot. Extend and wind the construction string to this post. Again, measure a distance equal to the length followed by the width, and wind and extend the construction string till you return to the first post. Here, tie down the string securely, and cut off the remaining part.

Keep in mind that you must try your best to fix either a square or rectangular perimeter. Therefore, the angle between any two of its sides needs to be as close to 90 degrees as possible. For this, you can use the method described in the 'Measurements' section, towards the end of this article.

Once completed, you will have a perimeter boundary for your project, which can help keep the construction work squared and symmetrical.

Step 3: Peripheral Hole Positioning and Digging

After you have readied the land and marked the perimeter, as described above, you can begin digging the holes for your foundation. Position the first hole at one corner of your plot within the perimeter boundary, and dig one which is at least 18 inches deep, using the post digger.

For a stronger foundation, one can even dig deeper up to 50 inches. The width of these holes will depend on the width of the concrete cinder blocks. Since the cinder blocks will have to fit inside the holes, each hole will need to be made wider than the cinder blocks themselves. Position the second hole by measuring a distance of 3 feet from the first hole along the perimeter string, and make sure that it is of similar dimensions as the first one. Repeat this process, and dig holes along the lengths of the perimeter, while leaving the widths untouched.

If you intend to build a square structure, then do this for any two parallel and opposite sides, leaving the remaining two as they are.

Step 4: Cinder block Placement

Once the hole digging is complete, pour some quantity of small rocks or gravel inside the first hole, and tamp it down using a gravel tamper or the end of a long stick/broom, to make it level as shown in the 1st part of the image below.

Now, as shown in the 2nd part of the image, add the concrete cinder blocks into the gravel-filled hole, stacking them one over another, till the top of the last one protrudes to a height of somewhere between 18 to 24 inches above ground level. Then, as seen in the 3rd part of the image, back-fill the remaining part of the hole with some of the mud that came out during the initial digging process. Once the hole is filled up to the surface, tamp it down to create a level surface. Thus, you have successfully completed your first pier. Repeat this procedure for all the holes, to build the pier system for your foundation.

One important thing to keep in mind is that, all the piers need to be at the same level, that is, at the same height above the ground surface. To ensure this, you can use a string level, as described in the 'Measurements' section of this article. If they aren't at the same level, the rock and gravel at the bed will have to be adjusted to bring them to the same level.

Another important thing is to make sure is that all the piers are exactly vertical. This can be checked using the plumb bob, the use of which too is described in the 'Measurements' section.

Step 5: Perimeter Width and Internal Pier Systems

For building the internal piers, all the same steps have to be used as described above. The internal piers are constructed for supporting the floor joists, and so can be referred to as joist-piers. Ideally, the spacing between two floor joists shouldn't be more than 2 ft. Therefore, the spacing between two lines of joist-pier holes should be maintained at 2ft. or less. The following figure should give you a clue as to how you should go about this task.

The digging of the internal joist-pier hole should be started from the perimeter width, going inwards. Thus, effectively, you will be digging lines of holes parallel to the perimeter length, which are spaced 2 ft. apart from each other. Note that for larger foundations, the spacing between the joist supporting piers can be up to four feet, so you need to dig holes accordingly.

Step 6: Floor Beam and Joist Setup

If you have successfully completed these 5 steps, you can truly give yourself a well-deserved pat on the back. The hard part is over, and now, all that remains is to use the lumber pieces to build the beams and joists.

Again, start with the perimeter, and build the beam structure along it. Fix the 2" × 6" wooden pieces, or those of your chosen length, onto the concrete piers along the boundary. You can use an angle cleat for this. First, nail the cleat securely to the concrete block, and then nail the pieces of lumber onto it. Repeat this along the perimeter while nailing each of the four separate pieces of lumber to the next one, until you get a four-sided connected beam structure running along the perimeter of the foundation.

Then, over the internal joist piers, install lumber pieces parallel to each other by nailing them onto the piers using the angle cleats, and also to the wooden beam at the ends. Do this for each line of joist piers, to finalize your floor-joist system.

After completion of the 6th step, you will be looking at a sturdy pier and beam foundation, made entirely by you.

If you are working in the sun, you are likely to sweat a lot. So keep yourself hydrated by drinking adequate amounts of water at regular intervals.

Plan and divide the work over several days to avoid over-exerting yourself.

Digging holes is labor-intensive work, and so is handling the heavy concrete blocks. Therefore, it is best to find a helping hand to assist you with this project.

Working with wood, nails, and hammers can cause injury. So always keep a first-aid kit at hand.

Don'ts

Constructing a pier and beam foundation involves a lot of work, so don't try and finish it in one go.

The foundation isn't strong enough to bear the weight of an entire house. Therefore, do not use it as a base to construct an occupied structure.

Measurement Methods

1) Perpendicularity

This method can be used to achieve near-perfect perpendicularity. It requires three persons. The first two wooden posts are fixed on the plot, as described in step 2, and the construction string is tied between them. Now, while the first person (a) stands near the second post, the 2nd person (b) extends the construction string in a tentative perpendicular direction to the 2nd post, up to a distance equal to the chosen width of the foundation structure. Then, using a red marker and a measuring tape, 'a' measures and marks 4 meter on the length of string between post 1 and post 2, and 3 meter on the length between post 2 and post 3, as shown in the figure.

According to Pythagoras' theorem, if the angle made by post 1, 2, and 3 is exactly 90 degrees, then the hypotenuse or the straight line joining the 4-meter and 3-meter marking should exactly be 5 meters. Now, (a) holds one end of the tape at the 4-meter marking, and a third person (c) extends and holds it on the 3-meter marking, thus measuring the distance between those two points. All this time, (b) keeps the length of the string stretched and taut. If the measurement taken by (c) is less than or more than 5 meters, then (b), while facing the 2nd post, will move to his left or right, till exactly 5 meters is obtained. After that, (b) will drop the plumb where he/she stands, and fix a pole on that spot to tie the string over.

2) Using the Plumb Bob

A plumb bob helps ensure that the structure you are building is perfectly vertical. It uses gravity to achieve 'true vertical' level. The following is a small description of how it works.

The string of the plumb bob is held at a certain height above the point where vertical level needs to be checked. Then, the plumb bob is dropped and allowed to hang down. Once it stops oscillating and becomes stable, it gives you a perfectly vertical line, represented by the string. This line is exactly parallel to the Earth's gravitational force. The following is an illustrative example, followed by instructions for using the plumb bob in a pier and beam foundation construction.

Drop the bob and allow it to just touch the ground level, while holding the string near the top of the pier. Ideally, all the concrete blocks that make up the pier should be at the same distance from the plumb string. If not, then the perpendicular distance between each block and the string is the measure by which it is 'out'. Adjusting the block or the gravel bed can ensure that the block, and subsequently, the entire pier becomes exactly vertical.

3) Using String level

String level can help build piers which are exactly at the same level with respect to each other. For using it, first hammer in two small nails on top of the two piers whose level needs to be checked. Tie a string in between them, and using a tape, measure its length. Divide this measurement value by half to find the central point of the string. Attach the bubble level at the central point.

If the bubble remains at the center, then both the piers are at the same level, if not, then you need to make adjustments to the gravel bed in one of the pier holes till the exact level is attained.

Using this simple step-by-step procedure, you can carry out a sturdy pier and beam construction, which can be used as a base to build any one of a number of useful structures. It might not be known as an architectural achievement, but it will surely make you feel proud once it is completed, knowing that it is a product of your own hard work.